Synthetic lubricants and power transmission fluids



United States Patent 3,538,001 SYNTHETIC LUBRICANTS AND POWER TRANSMISSION FLUIDS Herbert Gothel, Oberhausen-Sterkrade, Hans Feichtinger, Dinslaken, and Heinz Noeske, Oberhausen-Sterkrade Nord, Germany, assignors to Ruhrchemie Aktiengesellschaft, Obcrhausen-Holten, Germany, a corporation of Germany No Drawing. Original application July 8, 1965, Ser. No. 470,631. Divided and this application Nov. 20, 1968, Ser. No. 796,626

Claims priority, application Germany, July 10, 1964,

Int. Cl. ciom 1/52 US. Cl. 25249.6 18 Claims ABSTRACT OF THE DISCLOSURE A synthetic lubricant composition consisting essential 1y of at least percent of a diorthosilicate of the formula wherein A represents an alkylene radical having 2 to 24 carbon atoms, R represents a polyoxyalkyleneglycol ether radical having 1 to 4 ether oxygen atoms, R represents alkyl having more than 3 carbon atoms, and n has a value from 0 to 4, admixed with at least one other liquid impregnate which is preferably a mineral lubricant, a dicarboxylic acid ester, a phosphoric acid ester or an organic silicon compound. The lubricant composition may further contain antioxidants or other conventional materials in conventional proportions.

The application is a division of application Ser. No. 470,631, filed July 8, 1965, now abandoned.

This invention relates to new and useful synthetic liquid compositions or oils. More particularly, the invention is concerned with fluid or oily compositions comprising an alkandiol-diorthosilicic acid-(polyoxyalkyleneglycol-ether) -ester.

Synthetic lubricants and power transmission fluids are required to exhibit small changes in viscosity in response to changes in temperature and pressure. In particular, low viscosities at low temperatures and high viscosity indices are desirable. In addition, the volatility of the lubricant and power transmission fluid at high temperatures is required to be low in order that losses by volatilization are avoided. Further, the lubricants are required to possess high thermal and oxidative stabilities.

Further synthetic lubricants and power transmission fluids are required to exhibit satisfactory lubricating effectiveness and load carrying capacities to meet the demands of the mixed friction arising in the application where they are employed. The latter requirements of lubricant eflectiveness and load carrying capacities involve fluid bodies having high molecular weights. The heretofore known silicic acid ester lubricants and power transmission fluids have the disadvantages that they are susceptible to hydrolytic attack. Their viscosity is too low for most lubricating applications (for instance, their average viscosities at 98.9 C. are less than 3 cst. and, further, they exhibit considerable volatility at high temperatures so that losses by evaporation occur in use.

Although the effectiveness of silicic acid esters as lubricants is better than that of other organo-silicium compounds, their load carrying capacity has hitherto not proved satisfactory.

It is an object of the present invention to provide silicic acid esters of high molecular weight which combine the outstanding properties of high molecular materials with low viscosities at low temperatures.

3,538,001 Patented Nov. 3, 1970 It is another object of this invention to provide higher silicic acid esters of a particular type, the esters being in the nature of lubricating fluids, oils, and greases, and being characterized by small changes in viscosity with temperature and pressure.

A further object of this invention is to prepare novel compositions of matter comprising alkandiol-diorthosilicic acid (polyoxyalkyleneglycol ether)-esters which are useful as lubricants, power transmission fluids, damping fluids, etc.

Other objects and advantages of the invention will be apparent from the following detailed description there f.

It has now been discovered that these and other objects may be accomplished in part by the novel esters of the invention which have the following formula:

wherein A represents the alkylene residue of an alkandiol radical having 2 to 24 carbon atoms, R represents a polyoxyalkyleneglycol-ether radical having 1 to 4 ether-oxygen atoms, R represents an alkyl group having more than three carbon atoms, n has a value from 0 to 4 and wherein the substitutents R and R present in the molecule may be the same or different.

The fluid composition of this invention may be used alone or admixed with up to and preferably up to 50% of one or more liquid materials, e.g., conventional fluid bodies suitable for use as hydraulic fluids, lubricants, damping fluids, etc., as well as with the conventional fluid body additives, i.e., antioxidants, etc.

In accordance with the invention, diorthosilicic acid esters of the formula:

wherein A, R and R are as defined above, constitute broadly preferred di-orthosilicic acid esters.

The esters according to the invention containing R and R substituents having 8 and more carbon atoms are water-resistant, especially in the case of a steric shielding at the SiOC linkage. Their boiling points are above 470 C. at 260 torr and above 200 C. at 0.015 torr. Thus, isononadecandiol-diorthosilicic acid esters boil above 535 C. at 760 mm. Hg and above 260 C. at 0.015 torr.

The diorthosilicic acid esters as set out above are novel compounds. Thye may be prepared by the conventional methods employed for the production of diorthosilicic acid esters as known in the art. The diorthosilicic acid esters can be prepared, for instance, by reacting stoichiometric mixtures of suitable alcohols and ether alcohols with gaseous SiCl according to the disclosure of German Pat. No, 1,142,855 whereby the silicon tetrachloride is introduced at the bottom of the reaction vessel and hydrogen chloride evolved during the reaction is removed from the reaction vessel and reaction mixture by the application of vacuum or as disclosed in German Pat. No 1,180,359 which carries out the reaction of alcohol components with silicon tetrachloride in a subsequent turbulent phase in a bubble column reactor, see Example I below.

The advantages of the novel esters of the invention as lubricants and power transmission fluids are shown in Table I which follows, wherein the properties of certain of the esters of the invention are shown in comparison with those of known diorthosilicic acid esters of comparative molecular size. The following known esters corresponding to the formula:

(I) Ethyleneglycol-diorthosilicic acid-hexa-isodecyl-ester (II) 2,2-dimethyl-1,3-propanedioldiorthosilicic acid-hexaisodecyl-ester (V) Isononadecandiol-diorthosilicic acid-hexa-(3,5,5 trimethylhexyl -ester (VIII) Ethyleneglycol-diorthosilicic acid-hexa-isotridecyl ester were employed in the comparison.

The esters of the invention used in the comparison are the following:

4 conform to those where the R-groups comprise isodecyl groups.

The decrease of the viscosity indices due to the substitution of alkyl groups having increased carbon atoms is compensated for by the oxyalkylene-ether radicals present as R-groups in the molecule, as, for instance, diethyleneglycol-in-butyl-ether radicals.

Thus, the esters according to the invention, containing oxyalkylene ether radicals exhibit the advantages of esters known in the art containing alkyl groups having more than 8 carbon atoms, namely, small volatility and increased water-compatibility; furthermore, they possess the advantage of an excellent viscosity=temperature relationship as is peculiar to silicic acid esters having alkyl groups with less than 8 carbon atoms. The 2,2-dimethyl- 1,3-propane diol as well as the isononadecanediol-diorthosilicic acid esters having diethyleneglycol-n-butyl ether groups as R-groups and oxotridecyland oxodecyl-radicals as Rgroups possess viscosity indices, which are higher than those of conventional dibasic carboxylic acid esters, polyglycols, phosphoric acid esters and of other synthetic oils.

Generally, the viscosity of the esters at the comparison temperature of 98.9 C. increases with increasing molecular weight. Esters with branched A-groups, as, for in- TABLE 1 Alkanediol-diorthosilicic acid-ester scos y in w at is- Ppu Welding Moleeucoslty point, value load,

No. A R R n 1211 wt 98. 9 37. 8 40 54 index 0. kg.

I CH2CH2 OXO-ClnIIzr 6 1, 058 5. 9 23.03 3, 510 179 67 150/160 IL... CH2C(OH )2CH OXO-Ci Hn 6 1, 1 1 6 157 69 150/160 III- CHzCHz (CHZCH2O)211C4H9 0 1, 082 4. 0 13. 8 1, 231 8, 780 208 72 170/180 IV CH C(CH CH (CH CH O) nO H 0 1, 124 3. 32 11. 4 945 4, 810 185 76 170/180 V 0 11 -0 11 0 H 6 1, 213 23. 0 131 144 51 160/170 VI CHzCHz (CH2CH20)2-I1C4H9 0110-0131127 3 y 196 83 0 42 166 170/180 VII CH2C(CH3)2OH2 (CH2CH20)2I1C4HD OXO-C 131121 3 233 9 2 6 O 600 158 160/170 VIII CHzCHz Oxo-GnHzv 6 1, 310 10. 7 69. 0 57, 43 135 -55 150/160 IX Oxo-CgHas (CH2CH2O)2I1C4H0 Oxo-C 1 1121 3 1, 309 6. 2S). 4 2, 795 20, 700 161 -74 170/180 X 0x06 1135 (OH2CH20 211C4H9 0 1, 321 1 7 42. 0 5, 310 21, 800 167 -64 180/190 The expressions OX0-C H OXO-C13H27, OXO-C19H38, as used in the table, designate radical alcohols obtained from trimer-propylene, tetramer-propylene, and oleic acid by hydroformylation (oxo synthesis) followed by hydrogenation of the hydroformylation products.

The viscosity-temperature relationship and the range of the viscosity indices of the esters of the invention depend on the chain length and structure of the A, R, and R groups, as is clearly evident from the data of Table 1.

The comparison of the ethanediol-diorthosilicic acid ester with 2,2-dimethyl-l,3-propane diol esters having similar R and R' groups indicates that the ethanedioldiorthosilicic acid esters have higher viscosity indices. (In this connection compare the data for the esters (I) and (II) known in the art and the esters described in accordance with the invention, (III) and (IV) as well as (III) and (VI). The viscosity index decreases with increasing chain length of the substituents A, R and R (see, for example, the data obtained in connection with ester (II) with ester (IV), (VI) with (VII), (VIII) with (IX) and (X). The viscosity-temperature relation of the ester according to the invention, while somewhat less satisfactory than that of the esters having A, R and R groups of shorter chain length is, however, superior to that of the conventional synthetic lubricants.

The nature of the oxyalkylene-ether radicals directly influences the viscosity-temperature relationship. Ethanediol, 2,2-dimethyl-l,3-propane-diol and isonona-decandioldiorthosilicic acid-hexa-(diethyleneglycol-n-butyl ether)- ester possess a viscosity index of 208, 185, and 167, respectively. These values substantially correspond to those of the respective hexa-n-hexyl-esters.

In regard to volatility or boiling range, the esters containing diethyleneglycol-n-butyl-ether radicals (R groups) stance, derived from neopentylglycols, are on the other hand less viscous than those having the smallest alkylcue-bridge, namely, ethanediol-diorthosilicic acid esters (see Table 1).

If the R-groups of the esters according to the invention constitute oxyalkylene ether radicals, for instance, diethyleneglycol-n-butyl-ether-radicals, their viscosity decreases in comparison to corresponding esters. This decrease has an advantageous efiect on the viscosities of the said esters at -40 and -54 C., respectively. The viscosities of ethanedioland 2,2-dimethyl-1,3-propanediol-diorthosilicic acid hexa-(diethyleneglycol-n-butyl ether)-esters (esters (III) and (IV), respectively) at -54 C. lie far below the limiting value of 13,000 cst. which is true for dibasic carboxylic acid esters used as lubricants for gas-turbine airplanes, the said esters having viscosities of 3 cst. at 98.9 C. (see specification MilL-7808 D Accordingly, this is also true for the isononadecanediol-diorthosilicic-acid-hexa-(diethyleneglycol n butyl ether)-ester (X), whose viscosity at 40 C. lies also far below the limiting value of 13,000 cst. For this ester, which has a viscosity above 7.5 cst. at 98.9 C. the specification D. Eng. RD. 2487 2 is in effect.

Alkanediol diorthosilicic acid-hexa-oxyalkylene etheresters according to the invention with molecular weights below 900, as, for instance, ethanedioland 2,2-dimethyl- 1,3-propanediol-diorthosilicic acid-hexadiethyleneglycol n-butyl-ether)-ester, exhibit very low viscosities at 40 C. and -54 C., respectively; they range below 2500 est.

Military Specification Lubricating Oil, Aircraft Turbine Engine, Synthetic Base vol. 9.11, 1959.

-D1recti0rale of Engine Research and Development Material Specif. Vol. 16.55, 1900.

th testing methods are described in Gunclorson/Hart, Reinhold Publishing Corp. 1962, S. /156.

at 54 C. Their viscosity indices of 209 and 180, respectively, are very high. They are especially well suited as hydraulic liquids.

The load carrying capacity of the lubricating films of the several esters hereinbefore described was determined by means of the four-ball apparatus as described by Boerlage (Lexikon der Schmiertechnik, G. Voegtle, Franckhsche Verlagahandlung Stuttgart 1964). In the table, in the column Welding Value two values are given; the first number represents highest load in kg. which the lubricating film being tested withstands for one minute without alteration, while the second number represents that load at which the balls are welded, i.e., frozen, together.

As can be seen from Table 1, the welding values of the alkanediol-diorthosilicic acid esters according to the invention range from 160/170 to 180/190. The welding values of mineral oils range from 150/160 to 170/180. (See Lexikon der Schmiertechnik, 21.0., S. 543.)

Silicic acid esters according to the invention having long-chain A-radicals, particularly those containing oxyalkylene ethers radicals (for instance, derived from diethyleneglycol-n-butyl ether) as R-groups, are characterized by favorable welding values of 170/ 180 and higher. Alkanediol-diorthosilicic acid-hexa-alkyl-esters having alkyl-groups of less than 8 carbon atoms possess welding values of 140/150 and 150/ 1 60. Similar values are obtained with the majority of the conventional dibasic carboxylic acid esters as, for instance, di-oXooctyl-adipate, dioxooctyl-sebacate.

A further important criterion for satisfactory application of lubricants and power transmission fluids is their thermal stability. The latter was tested according to specification D. Eng. RD. 2487 as specified for lubricants for gas-turbine airplanes on the basis of dibasic carboxylic acid esters. 100 ml. of the materials to be tested were heated at 280 C.:l for 24 hours. At intervals of 6 hours, a sample of the material was tested for change of its viscosity at 37.8 C. Any increase should never exceed 20%. The values of the percentage change of the viscosity at 37.8 C. were plotted against the whole testing period of 24 hours and are set out in Table 2. The neutralization number (nN) as well as the hydroxyl number (OI-IN) are also listed in Table 2.

The ester of the invention is present in any admixture in an amount equal to at least 5% and preferably at least of the resulting admixture.

An especially well suited oxidation inhibitor is phenothiazine. It can be added in amounts from 0.1 up to 1.5% by weight, dependent upon the quantity of the lubricant.

Conventional additives for improving the oiliness of the lubricants consisting of or containing the esters of the invention, as for instance tricresylphosphate may be added in amounts from 0.1 up to 3% by weight dependent upon the quantity of the lubricant. It is not however necessary to employ these additives, since the esters according to the invention per se exhibit outstanding lubricating action.

The following examples are intended to illustrate the invention and are not be interpreted as limiting the same.

EXAMPLE 1 A so-called bubble-column reaction vessel consisting of a vertical glass tube having an interior diameter of 63 mm. and a height of 480 mm. provided with a glass frit (Jena apparatus glass, coarseness 2) its bottom, was charged with a mixture consisting of g. glycol, 529 g. isotridecanol and 428 g. diethyleneglycol-n-butylether, which had previously been carefully dried. From a dosing vessel, 272 g. silicium-tetrachloride was applied dropwise into an evaporator coil, which was gastight connected with the said reaction vessel by a conduit joining it below the said glass frit. The SiCL, vapors were sucked through the glass frit under a vacuum of 180 torr into the reaction vessel. The liquid mixture, preheated to 40 C. was heated at 58 C. by the reaction heat evolved in the bubble column formed in the reaction vessel by the ascending vapors of silicium tetrachloride and hydrogen chloride evolved during the reaction together with the liquid reactants. The reaction was complete after 120 minutes. Hydrogen chloride dissolved in the reaction was removed at a vacuum of 20 torr under introduction of nitrogen from the reaction mixture heated to 110 C. (Thereafter the Beilstein-reaction was negative.) The non-reacted excess liquid components (162 g.) were distilled off at 0.09 torr under heating up to 180 C.

A distillation residue 890 g. ethanediol-diorthosilicic acid-tri-(diethyleneglycol-n-butylether) tri-(isotridecyl)- It can be seen from the values given in Table 2 that the alkanediol-diorthosilicic acid-esters according to the invention generally exhibit a high thermal stability.

The esters according to the invention can be used alone or in admixture with other fluid bodies known in the art as lubricants and power transmission fluids, as, for instance, with mineral lubricants, dicarboxylic acid esters, phosphoric acid esters, organosilicium compounds of different structure as well as with conventional oxidation inhibitors and other conventional additives. For instance, they may be admixed with (1) a liquid dicarboxylic acid ester or with (2) a liquid organo-silicium compound as for example,

a methyl polysiloxane or (3) with both phosphoric acid ester and an oxidation in hibitor.

ester were obtained; its Si content was determined to 4.72% (calculated 4.68%). The following data of the product ester were determined: density d =0.954, refraction index n =1.4508; viscosity at 989 C. 6.83 cst., at 37.8 C. 30.0 cst., at 40 C. 7420 est; viscosity index 166, flow point (or setting point) at 64 C., flame point at 263 C.

In analogous manner other esters according to the invention can be prepared.

EXAMPLE 2 50 parts by volume of a known dibasic ester, bis-(isotridecyl)-adipate, were admixed with 50 parts by volume isononadecanediol-diorthosilicic acid hexa (diethyleneglycol-n-butylether)-ester (ester (X) of the invention).

7 This ester mixture meets the demands for turbopropengine lubricants according to D. Eng. RD. 2487 Due to the admixture of the esters of the invention, essential properties of dibasic esters are improved: The viscosity at low temperatures is lowered, the viscosity index and the load carrying capacity are increased.

These improvements can be seen from the values given in Table 3 which follows wherein the properties of the hereinbefore described ester mixture (designated admixture 50/50 percent by vol.) are shown in comparison with those of its components.

2. A lubricant according to claim .1 wherein said lubricating oil is at least one member selected from the group consisting of mineral lubricants, dicarboxylic acid esters, phosphoric acid esters, and siloxanes.

3. A lubricant according to claim 1 additionally containing an antioxidant.

4. A lubricant according to claim 1 wherein said diorthosilicic acid ester is ethyleneglycol-diorthosilicic acidhexadiethyleneglycol-n-butyl-ether) -ester.

5. A lubricant according to claim 1 wherein said diorthosilicic acid ester is 2,2-dimethyl-1,3-propanediol- TABLE 3 Viscosity in est. at 0. Welding Viscosity Setting Flame value load (14 08. 9 37. 8 40 index point, 0. point, C. in kg.

Bis-(isotridecyl) adipate 0. 914 5. 4 30. 7 V 20. 030 122 55 255 150/160 Ester X 0. 990 10. 7 42. 0 5, 310 167 --64 272 180/190 Admixture 50/50 percent by vol 0. 953 7. 6 40. 16 10, 890 144 59 261 170/180 EXAMPLE 3 EXAMPLE 4 50 parts by volume of the mineral lubricating oil mentioned in Example 3 were admixed with 50 parts by volume isononadecanediol diorthosilicic acid hexa (diethyleneglycol-n-butylether)-ester (ester (X) of the invention). A comparison of the lubricant so obtained (here- 'i'nafter designated admixture 50/50 percent by vol. M) 40 with the said mineral oil and the ester according to the invention has also been set out in Table 4 which follows.

diorthosilicic acid hexa-(diethyleneglycol-n-butyl-ether) ester.

6. A lubricant according to claim 1 wherein said diorthosilicic acid ester is ethyleneglycol-diorthosilicic acidtri (diethyleneglycol n butyl ether)-tri-(iso-tridecyl)- ester.

7. A lubricant according to claim 1 wherein said diorthosilicic acid ester is 2,2-dimethyl-1,3-propanedioldiorthosilicic acid tri-(diethyleneglycol-n-butyl-ether) -tri- (iso-tridecyD-ester.

8. A lubricant according to claim 1 wherein said diorthosilicic acid ester is isononadecandiol-diorthosilicic acid tri (diethyleneglycol-n-butyl-ether)-tri-(iso-decyl)- ester.

9. A lubricant according to claim 1 wherein said diorthosilicic acid ester is isononadecandiol-diorthosilicic acid-hexadiethyleneglycol-n-butyl-ether) -ester.

10. A lubricant comprising at least by weight of a liquid diorthosilicic acid ester of the formula:

TABLE 4 Viscosity in est. at C. Viscosity Flame Setting d4 98. 9 37. 8 -17. 8 index point, 0. point, 0.

Mineral lubricating oil 0. 990 11. 5 130 25, 100 79 238 19 Ester III 4. 0 13. 8 135 208 245 72 Admixture 75/25 percent by vol 9. 03 67. 9 4,100 116 239 21 Ester X 10. 7 42. 0 521 167 272 -62 Admixture 50/50 percent by vol. M 11.0 76. 65 3, 910 129 248 23 The mixtures of Examples 3 and 4 represent motor oils which meet the demands for several classes according to SAE classification (Society of Automotive Engineers).

Due to the addition of the esters of the invention to mineral lubricating oils, essential properties of these oils are improved: Their viscosity indices are increased (as for instance for 37 units at an addition of 25% by vol. of the ester of the invention). Their viscosities, especially at low temperatures, are diminished. The flame points are raised and the setting points are lowered. Further on, the lubricating action is improved.

We claim:

1. A lubricant comprising 5% to by weight of a liquid diorthosilicic acid ester of the formula:

wherein A represents the alkylene residue of an alkanediol radical having 2 to 24 carbon atoms, R represents a polyoxyalkyleneglycol ether radical having 1 to 4 ether oxygen atoms, R represents alkyl having more than 3 carbon atoms, and n has a value from 0 to 4 admixed with 95% to 5% of another lubricating oil.

wherein A represents the alkylene residue of an alkanediol radical having 2 to 24 carbon atoms, R represents a polyoxyalkyleneglycol ether radical having 1 to 4 ether oxygen atoms, R represents alkyl having more than 3 carbon atoms, and n has a value from 0 to 4 admixed with a lubricating amount of another lubricating oil.

11. A lubricant according to claim 10 wherein said lubricating oil is at least one member selected from the group consisting of mineral lubricants, dicarboxylic acid esters, phosphoric acid esters, and siloxanes.

12. A lubricant according to claim 10 additionally containing an antioxidant.

13. A lubricant according to claim 10 wherein said diorthosilicic acid ester is ethyleneglycol-diorthosilicic acid-hexa- (diethyleneglycol-n-butyl-ether) -ester.

14. A lubricant according to claim 10 wherein said diorthosilicic acid ester is 2,2-dimethyl-1,3-propandioldiorthosilicic acid hexa-(diethyleneglycol-n-butyl-ether) ester.

15. A lubricant according to claim 10 wherein said diorthosilicic acid ester 'is ethyleneglycol-diorthosilicic 9 acid tri (diethyleneglycol n butyl ether) -tri-(iso-tridecyl)-ester.

16. A lubricant according to claim 10 wherein said diorthosilicic acid ester is 2,2-dimethyl-1,3-propanedioldiorthosilicic acid tri-(diethyleneglycol-n-butyl-ether) -tri- (iso-tridecyl)-ester.

17. A lubricant according to claim 10 wherein said diorthosilicic acid ester is isononadecandiol-diorthosilicic acid tri (diethyleneglycol-n-butyl-ether)-tri-(iso-decyl)- ester.

18. A lubricant according to claim 10 wherein said diorthosilicic acid ester is isononadecandiol-diorthosilicic acid-hexa- (diethyleneglycol-n-butyl-ether) -ester.

References Cited DANIEL E. WYMAN, Primary Examiner 10 W. H. CANNON, Assistant Examiner US. Cl. X.R.

Kreisler 77l.l-Div.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTIQN Patent No. 3 ,538,001 Dated Nov. 3, 1970 Invent r(s) HERBERT ET AL It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

The following errors were incurred by the Patent Office Column 2, line 53 change "Thye" to They Column 3, (Table ]l No. V No IX correct the formula n 1 n No. x 0x0 C 8 to read Orzo-0 E1 Column 3, line 58 Change "VI" to --VII-- mam ma smusn W89 1971 Am Eamaumcch h. Mr. :3.

Attesting Officer mum of atents 

